1. Wittgenstein Centre for Demography and Global Human Capital, Vienna A1090, Austria.
2. World Population Program, International Institute for Applied Systems Analysis (IIASA), Laxenburg A2361, Austria.
3. Vienna Institute of Demography of the Austrian Academy of Sciences, Vienna A1040, Austria.
4. Department of Applied Statistics and Research Institute on Human Capital and Development, Vienna University of Economics and Business, Vienna A1090, Austria.